Why do some parts of the human body (example: alveoli of lungs, skin, intestines) are said to cover a big area when stretched out, but can also fit inside a small human body?

Question

Why do some parts of the human body (example: alveoli of lungs, skin, intestines) are said to cover a big area when stretched out, but can also fit inside a small human body?

In: Biology

Answer 1

Clench your fist, take a really long ribbon and push it all down into your clenched fist. See how it fits, despite being so long? Because it’s so thin (alveoli etc is even thinner, compared to how long it is a lot of it can fit in a tight space